Not
all nematodes or roundworms are
harmful to human activities,
actually two species in particular
are very beneficial in the Florida
garden. The word nematode is made up
of two Greek words: Nema
which means "thread" and ode which
means "like". This word
describes the shape of these microscopic
worms which are "thread-like".

Nematodes
are
entomopathogenic, which
comes from the Greek words
entomon, meaning "insect"
and pathogenic,
meaning "that which causes
suffering". Entomopathogenic
nematodes are worms "which cause
suffering" to insects and do not harm
humans, pets or other animals.

How
Beneficial Nematodes do their Job

Juvenile
nematodes hunt and infect host insects.
After entering an insect host through
its mouth, anus or
breathing holes (spiracles) -- Heterorhabditid nematodes can also
pierce through an insect' s body wall --
the juvenile nematodes release a bacteria of the genus Xenorhabdus
(steinerernematides) or Photorhabdus (heterorhabditids)
which kill the host insect in 24 to 48 hours
by liquefying its insides.

There is a
symbiotic relationship between the
nematodes and bacteria --
nematodes provide shelter and
transportation for the
bacteria which kill the insect host and
provide nutrients to the nematodes.
Together, the nematodes and bacteria
feed on the liquefied host and
reproduce inside the the dead insect's
body. When nutrition stores inside the
host insect begin to run out, the adult
nematodes produce new infective
juveniles adapted to withstand
environmental conditions outside the
host insect.

After about a week,
hundreds of thousands of infective
juveniles emerge from the hollow carcass
of the host insect and search for
new hosts carrying with them an
inoculation of bacteria that starts the
lifecycle of the nematodes and bacteria over again.

Live nematodes from
ARBICO Organics filmed under a microscope. To give a rough
idea of how small these worms are (you cannot see them with the naked eye),
they are wiggling around in a drop of
water -- I filmed only a tiny portion of
that drop.

Heterorhabditis bacteriophora
nematodes roam deeply through the
soil searching for potential insect
hosts while Steinernema
feltiae are more sedentary
and wait for host insects to
approach them. Some
Steinernema hunt by raising
up off the soil surface to attach to
passing insects. Others are able to
jump on passing hosts by forming a
loop with their body that propels
them through the air allowing them
to attack their host insects.

Nematodes are shipped in a finely ground
moist clay powder that is added to
water. This nematode solution is applied
using a watering can, hose end sprayer,
backpack or pump sprayer or through
irrigation or misting systems. The best
times to apply the nematode solution is
early in the morning or before dusk when
the temperatures are cooler and the sun
is not as bright. The soil where the
solution is to be applied should be
moist at the time of application and
lightly watered immediately after
application. After application, regular
watering of the treated area will
provide sufficient moisture. Generally
speaking, water every 3-4 days if
rainfall does not occur. It is not
beneficial to spray the nematode
solution on plants as these round worms
are soil dwellers.

Nematodes are recommended for use
whenever larvae or grubs of insects
targeted for control are present during
the spring and fall months. Because
larvae feed on plant roots, beneath the
soil surface, severe damage can be done
before realizing there is a problem.
Look for signs of an adult insect, such
as leaf-notching. If adult insects are
present, their eggs will be hatching
soon. Keep in mind, one application of
nematodes may not eradicate a population
of insects that has become established
over a period of years.

Beneficial nematodes can be stored in a
refrigerator for up to two months. The
best way to store unused portions is to
place them in a large shallow storage
container and cover with about ½ inch of
water. This is to ensure that they do
not dry out and that the maximum area is
exposed to the air so they can breathe.

It is best to make at least two nematode
applications separated by 7-10 days in
order to stagger the life cycles of the
nematodes and to assure complete
coverage. In cases of severe insect
infestations, applications should be
made every 7-10 days or until
infestations subside.